Preparation of heavy metal soaps



' Patented Feb. 18, 1947' 2,416,074

. I I 2,41ao'z4i PREPARATION or HEAVY METAL soars I 7 Arthur G. Weber, Bellevue Manor,

and Clement H. Hamblet, Gordon Heights, DeL, assignors to E. I. du Pont de Nemours 8: Company, Wilmington, DeL, a. corporation of Delaware y f No Drawing,

I invention relates toa process for-the prep- Application September 21, 1943,- Serial No. 503,268 Y Q' a Claims. '(Cl. 260-414) i v The process of the invention is adapted to the aration of metallic salts of organic acids and,

' more particularly to .the"preparation ofmetal soaps of the fatty acids.

Various methods have beenproposed for the sures may be used.

preparation oi heavy metal salts of any. organic acid ester or mixture thereof. As examples of I converter the organicacid esters that may be employed in accord with the processof the invention are esters preparation of the metallic salts of the organic of the: fatty acids; acetic, propionic, butyric; acidssuch, for example a the reaction of the 'caproic lauric, .palmitia; stearic; ricinoleic, organic acid with a heavy; metal oxide or carmelissic, and-other. members of the fatty acid bonate' or by the. exposure of the metal to the series as well as the esters of the coconut oil, corn warm vapors of the organic acids, the latter pro- 01], cottonseed,- QiLrape'seed oil and-similar vegecedure being employed for the preparation of table oils; esterspfthe hydroxy acids such, for white lead, requiring many days and in some example, as glycoliclacld,lactic-acid, andt'artaric cases weeksin processing These slow and tedious. acid; as well as'mono, and-polyesters of the polyprocesse are unsuitable for rapid economical forv carboxylic acids such, for;example, as. oxalicacid, mation of the heavy metal salts of organic acids. glutaric acidyandadipic'acid; and the esters of An object of the present invention is to provide 7 the unsaturated acidssuch,{for example, as ac'ryla process for the preparation of metalsalts of lo acid and .methacrylic acid, as well as the esters organic acids. Another object of the invention of thearomatic acids such, for example, as benis toprovidea process wherein organic acid esters -zoic acid and napththenic" acid. 2 can be'converted to the corresponding metal salt Any' suitable ester may be used such for exby direct contact with a metal. A further object ample :as. the methyhethyL propyl and higher, of the invention is to provide a processwherein allryl esters of thea'boveacids togetl'i'er'with their a the organic acid esters and more particularly the glyceride and compounds similar tothe glycerfatty acid esters are converted to lead salts by ides suchas the monoand-di-acid esters of the direct reaction'with lead in the presence of oxy-' glycols. Inasmuch as the-glycerol'and'glycol de gen, Other objects and advantages of the invenrivatives of the organic acids are in efle'c-testers tion will hereinafter appear. they will in this pecification'and inthe appended.

The above obj a accomplished in ccor claims be included under the generic termestersj i with the'broadest aspects of the invention 'by a The heavy metals that maybe used. include process wherein an organic acid ester is heated 0 such metals-as copper, cadmium, zinc, iron," in the presence of water as such or' as water vapor nickel, silver, tin and. especially-'- lead although with a heavy metal while inflcontact with oxygen. other salt forming metals may be reacted with More specifically, the process may be conducted the above compounds for the preparation of the by passing an oxygen-containing gas such as air, corresponding acid salts. a 1 the Organic acidv and water into a converter Water. should preferably be present in excess I charged with metal pellets,-gas and ester flowing of the amount necessary to react 'with the orco-current or, countercurrent through the conganic acidesten'i'. e., one-half a mole for the verter. I Q ester of a-monobasic acid ester, one mole for a The temperature of the reaction may very di-ester -vyof'a dibasic acid or a di-acid glycol e'sthrough wide limits according to the nature of 40' ter, or ut another way. one-half amole for each the organic ester used and the heavy metal with ester group present. The' inolare-xcess may .be which it is-to react, the unsaturated acid esters 10 to '50 times that stoichiometrically required. being'prefemmy t d at a w r t p rature, It will be understood that in thevclaims the'use than the saturated acid esters to inhibit degradaoi the word water will mean water as; such tion. When normally solid acid esters are treated r or a its vapor. f j they should be heated at least to that tempera- The process may be carried'out by a: continuous ture at'which they are fluid in order that the or discontinuous procedure. The former may, oxygen or oxygen containing gas can be easily for example, be illustrated by theju'se ofa conbubbled through them. Generally speaking, howverter of considerably greater length than cross ever, temperatures may range between and section disposed inavertical posltionand'charged 200 C. and more specifically for the fatty acid with pellets ofa metalwhich may bein the form esters, temperatures ranging betweenand 150 of chips, flakes, or" metalv pellets-of a" suitable C. witha preferred'range for the preparation of r diameter'such, as forexample, from /gto inch. the lead soaps of the fatty-acids between and v The organic acid, este to be converted to the 1209 C. Atmospheric or superatmospherie pres 55 metal salt and water arerintroduced into the together with an oxygen containing converter.

3 m such as air and the reaction within the converter maintained at the optimum temperature for the particular type of ester being converted. When carried out in this manner the ester may be introduced at the top of the converter and the product collected from the bottom while air is bubbled up through thedescending ester and the process thereby conducted under countercurrent flow conditions, the spent air being allowed to issue from the top of the converter carrying with it any excess water and the alcoholformed during the reaction. Contrariwise, both ester and air can be introduced into the bottom of the converter to give cocurrent flow, the product as well as the spent air, alcoholand water formed issuing from the top of the converter. To enhance the flow of fluids within the converter a portion of .the reactants may be pumped from the top of the converter and reintroduced into the bottom thereof, the velocity and turbulence of the flow within the converter being regulated in part by the amount and degree of this recycled material. As will be appreciated by those skilled in the art the recycling may be conducted in the reverse order that is by taking the product from the bottom and reintroducing it intothe'top of the converter and a further modification may be efi'ected by removing the product from the intermediate positions and returning it through intermediate positions to the converter. If desired, the throughput of ester may be adjusted tothe length of the converter inorder that substantially all of the ester is converted to its salt as it emerges from the converter.

The process may likewise be conducted batchwise which may be efiected by charging a con verter such as that described above or any suit-. able vessel with the metal particles and the ester to be reacted,'the ester is raised to reaction temper'ature and the reaction continued until all of the ester has been converted to thesalt Whereupon it is discharged from the converter. Throughout the reaction air or oxygen or an oxygen containing ga is bubbled through or otherwise dispersed into the liquid. During batchwise processing it is likewise desirable to recirculate the reactants through the vessel which may be accomplished by an outside circuit provided with a suitable pump whereby the reactants are removed and returned tothe vessel in order to maintain a constant, preferably turbulent, flow within the vessel.

When a converter of greater length than cross section is employed which prior to operation is charged with the metal pellets and water-insoluble ester and water introduced and/or alcohol formed gradually settles to the bottom of the converter. than the water, the latter tends to collect in the bottom of the converter during the initial stages of: the reaction. Asthe reaction proceeds and the metal'salt increases in concentration in the converter the positions of water and ester product are reversed since the salts are invariably heavier. Unfortunately, this reversal in position takes place rapidly-with the evaporation of an appreciable part of the water and with the result that unless dueprecautions are taken a large part of the charge will be blown from the It has been found that the above disadvantageous result can be eliminated by recycling some of the material from the converter through Since the ester is generally lighter it possible to conduct the reaction without loss of products from this cause.

The reaction of an ester with a metal is exothermic and consequently'after'the reaction has been initiated no further heat input is required :heat in thespent gase but it has been found that in addition to these heat controlling means it is often desirable to provide excess water utilizing its sensible and latent heat to control the reaction within the preferred temperature range.

As has been indicated the process is applicable to the conversion of any organic acid ester to it metal salt. Inasmuch as some metal salts are soluble in the ester from which it is derived while others are not, a different procedure is recommended when metal salts of different types are to be made. v

When the metal salt is soluble in the ester in which it is made it is merely necessary to maintain the temperature of the reaction above the transition point of the mixture or above that temperature at which the metal salt precipitates. In some cases, the solution of ester and salt can be withdrawn from the converter, cooled down to precipitate the salt, the salt separated by filtration and the ester returned to the converter. Analogous to the latter type of procedure is that used for the preparation of salts which are relatively insoluble in-the ester. Under such circumstances it is usually desirable to effect the reaction in a mutual solvent for the ester and salt from which the salt can be crystallized or otherwise separated after withdrawing it from the reaction converter the unreacted ester being returned to the reaction.

The examples which follow illustrate embodiare passed intothe bottom of the tower while spent air, water vapor, the unconverted organic reactant and lead salts passed out of the top of the tower into a separator from which the spent air and water as vapor are discharged to the atmosphere. The unconverted organic acid ester together with the salt thereof is returned to the bottom of the tower. A valve is provided in the top of the bottom of the recirculating line through which the lead soaps formed are discharged after the desired conversion had been reached.

. Air is introduced into the tower at a space velocity of and the reaction mixture is heated to a temperature of approximately C. and; 85% of the acyl groups present in the coconut oil fatty acids is converted in from two to three hours to lead soaps.

Example 2.A glass jacketed tower with an internal diameter of 1.9 cm. and a height of cm. is completely filled with lead fragments of about A," diameter. Air, water and the organicacid ester are passed into the bottom of the tower while spent air and urireacted water passed out of the top of the'tower from which the spent air and water as vapor are discharged to the atmosphere. A valve is provided in the recirculating line through which the lead soap formed was discharged. The tower is charged with a mixture of 148 g. of esters of coconut oil fatty acids made by the esterification of the acids with the corresponding alcohols and 0.15 part hydroquinone and the mixture heated. to a temperature of 150-160 C. while air is forced up through the tower at the rate of approximately 15 partsv per hour. The exit gas is analyzed and found to con tain from 20 to 20.7% oxygen indicating that substantially none of the ester had been converted to the lead salt. Forty one moles of water are then introduced into the tower per mole of ester and the addition of air continued at the same rate as before. Substantially immediately the exit' gas from the tower analyzed 11.4% oxygen indicating that the reaction had set in. After approximately eight hours of operation the tower is discharged and it is found that nearly 100% of the ester had been converted to the corresponding lead salt of the coconut oil acid.

Example 3.The tower of Example 2 is charged with lead pellets. 125 g. of methyl oleate and 0.18 part of hydroquinone, the reactionbeing maintained at 140 C. More than a stoichiometrical excess of water is added and air is introduced at a rate of about 15 parts per hour. After approximately eight hours o eration an excellent yield of the lead salt is obtained.

As shown by the examples, the rate of oxy en flow may be varied and it has been found that this variation may range between a space velocity of and 100. space velocity being defined as the unit volume of air passing per hour per superfic al volume occupied by'the metal particles in the tower, the fluid volumes being determined under standard temperature and pressure conditions. While the examples have described the use of air. other inert gas-oxygen-mixtures may be employed or for that matter pure oxygen may be used.

The use of an antioxidant is highly advantageous when unsaturated organic esters are converted to. their salts. 'The evolution of carbon dioxide indicates degradation of the acid or salt during the reaction and it has been found that the presence of an antioxidant inhibits and usually entirely eliminates this degradation. Suitable examples of antioxidants which may be employed are in addition to the hydroquinone described in the examples pyrogallol, phenoLphenyl-alphanaphthyl amine. mesitols, and other suitable antioxidants. The antioxidant may be used in amounts ranging between 0.005 and 2% by weight based on the organic acidwith a preferred range particularly for hydroquinone between 0.01 and 0.02.,

We claim:

1. In a process for the preparation of lead soaps of fatty acids by reacting.esters of the higher fatty acid with lead the step which comprises passing an alkyl ester of a higher unsaturated fatty acid and water over comminuted lead while bubbling oxygen through the liquid acid at a temperature between 50 and 200 C.

2. The process of claim I conducted in the presence of an antioxidant selected from the roup consisting of hydroquinone, pyrogallol.

phenol. phenyl-alpha-naphthylamine and the mesitals. I i

3. In a process for the preparation of heavy 6 metal oleate by reacting an ester of oleic acid with a heavy metal the step which comprises passing an. alkyl ester of oleic acid and water over a comminuted heavy metal while bubbling oxygen through the liquid ester, the reaction being conducted at a temperature between 70 and. 150 C.

4. In a process for the preparation of a heavy metal soap of coconut oil acids by reacting the esters of coconut oil acids with heavy metal, the step which comprises passing alkyl esters of coconut oil acids and water over lead pellets while esters of fatty acids containing unsaturation with a heavy metal the step which comprises passing an alkyl ester of a fatt acid containing unsaturation and water over a comminuted heavy metal while bubbling oxygen through the liquid ester, the degradation of the fatty acid esterand its soap being inhibited by the presence of hydroquinone.

7. In a process for the preparation of heavy metal soaps, the step which comprises passing an ester of a higher fatty acid and water over a comminuted heavy metal, at a temperature between 70' and 150 C., while bubbling oxygen through the liquid ester.

8. In a process for the preparation of lead soaps, the step which comprises passing over comminuted lead, an alkyl ester of a higher fatty acid and from 10 to 50 times the stoichiometrically required amount of Water for reacting with the ester, while bubbling oxygen through the ester. the reaction being conducted at a temperature between 50 and 200 C.

9.. In a process for the preparation of heavy metal soaps, the step which comprises passing over a comminuted heavy metal water and an alkyl ester of' higher fatty acid which is in the liquid phase, by virtue of a mutual liquid solvent for the fatty acid ester and for the metal soap formed therefrom, while bubbling oxygen through the solution of the ester and soap at a temperature between 50 and 200 C.

ARTHUR G. WEBER. CLEMENT H. HAMBLET.

REFERENCES orrED The following references are of record in the 'file of this patent:

STATES PATENTS OTHER REFERENCES 1 Perry, Chemical Engineers Handbook," ed. 2. 1941, page 2096. 

